There are numerous types of flush-embedded paving blocks which more or less effectively perform the following functions:
break up the smoothness of the contact faces in order to prevent longitudinal and transverse displacement of the paving blocks with respect to one another; provide an enlarged perimeter of the paving blocks and therefore their contact surface area in order to increase the friction and thus the resistance to individual collapse under load; and
break up the rectilinearity of the joints in order to prevent them from acting as a hinge in the plane of the surfacing and in order to combat the rutting phenomenon.
However, these three objectives can only be achieved if each paving block is placed in a position where it is impossible for it to move away from its neighbors, which is achieved only by perfect abutment of the whole, ensuring a horizontal transference of load. However, this is not always possible. For example, one can invention areas on roofs, where the thickness and the load are limited and the possibilities of counter-abutment are all the more reduced, or also cycle tracks and other narrow roadways where the extent of the borders is disproportionate to the surface area.
However this may be, any rutting is reflected in traction on the upper or lower surface of the surfacing, according to whether it is situated in the raised zone or the depressed zone of the the ruts.
Known from the document FR-A-2608 is an interlocking paving block which is cruciform in shape and the four arms of which are of the same width, the length of one arm being equal to its width. Such a paving block is only capable of withstanding a thrust stress.
Described in the document EP-A-0 377 460 is a paving block for surfacing an area of ground and which is of square shape, comprising on its lateral surfaces spacers which allow lawn to be positioned between the fitted together paving blocks.
These projections coincide or overlap one another in adjacent paving, blocks according to the size allowed for the lawn. Here there is no question of flush fitment for withstanding thrust or traction stresses.
However, the necessary limitation of the angle of flare of the arms, on plane of excessively reducing the points of connection, means that the flush fitment can no longer be very effective.